I have had non-stop problems with my libby and i have had it for only five months. Blew a head gasket and had a shop fix them and replace the radiator. But it still has a rough idle (runs perfectly fine when driving on roads, freeway etc). Then i turned on the A/C and its squeaking noises came from the engine compartment. Turned off A/C and the noise went away but the code is still there. The shop is a bunch of scumbags who told me its not there problem, but i picked it up yesterday??!! I dont know the code yet because this just happened twenty minutes but i figured i would jump on here and ask for some suggestions.

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2002 Jeep Liberty Sport

ok just pulled the code it is P0138-o2 sensor circuit high voltage (bank 1, sensor 2). anyone know anything about this? im going to take it back to the shop but I would rather not because i get nothing but lies from them and i dont trust them at alll. but i already paid them and i dont have another 1500 bucks to spend.

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2002 Jeep Liberty Sport

Thast an easy one to fix and cheap to get, I think mine was 30-35 at most for the part, took all of 5 minutes to change out, including getting the tool box out! If it needs replacing
Its located near the transmission cross member
***Oxygen sensor input voltage maintained above normal operating range

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MUDD'S MOTORSPORT'S We do IFS lift installs ,
03 OVERLAND EDITION /Kilby-Skidrow-Mopar-4XGuard skids/ 2.5 inch TOTAL CONTROL JBA coilovers -JBA Arms/MOABS-31 FALKEN WILDPEAK AT3W / 4.10's etc, 04 Kilimanjaro Edition loaded, plus 05 KJ limited

O2 sensors are mounted on your exhaust system and monitor how rich/lean your engine is running, the computer uses this information to adjust the (for lack of a better description), "fuel mixture". The bank is the side of the engine. A "V" engine has two banks, bank 1 being the side of the engine that contains cyl 1, and bank 2 is the other one, newer vehicles have numerous sensors to monitor different areas in the exhaust. Sensor 1 is the sensor closest to the engine, before the catalytic converter, and sensor 2 will be after th catalytic converter. So a bank 1 sensor 2 high volts code means the sensor after the catalytic converter is producing a higher than normal voltage signal. This can be casued by: A bad 02 sensor, A bad catalytic converter, A problem with the reading on the forward sensors, And sometimes a vaccuum leak will cause a code, but usually on the front sensors, the #2 sensors monitor the working of and efficiency of the converter in relation to the front sensors.

Since you had the head gaskets replaced, water leaking into the engine and through the exhaust can easily damage the sensors, and possibly the converter. A good shop with any knowledge should be able to pull up the voltages of all the sensors and decide if its the sensor or another problem.

As tommudd said, their usually pretty cheap, I always spray some penetrating oil on the old sensor to make sure it doesnt strip the threads when you unscrew it.
A shop that didnt want to adress this issue at all would definitely not be my shop anymore. I understand stuffs not free, but at least discuss what could cause it with me. Anyway hope this at least gets you on the right track.

thanks tommudd and JustinP for the info it helped out alot! so now where im is that I still have a misfire so the shop basically gave it to me exactly how I gave it to them. I refuse to take my Libby back them since because all they have done to me is lie and i have had issues with them since day one. so I already called my credit card company and put a stop payment on it (only put 800 on the card and paid 400 cash). And im going to have to take it to a new shop in the morning and start all over again. I will never use craigslist to find a cheap shop again. Anyone know of a trustworthy shop in the phoenix area?

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2002 Jeep Liberty Sport

Ok after just checking the code again it showed p0303 Cylinder 3 misfire detected this time.

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2002 Jeep Liberty Sport

Well thats bad news, but not the worst neccessarily. Since its a definitive cyl 3 misfire and not a random/multiple, you can start diagnosing the 3rd cylinder directly.

If this a 4 cylinder, I believe you have 1 coilpack and of course 4 sparkplug wires, since your old mechanic just had the engine torn apart, check to make sure the wires are fully seated on the spark plugs and fully plugged into the coil pack. Also move the wire around and make sure its not laying on anything on the engine. Youd be surprised how many technicians forget to reattach wire retainers and clips. If all of this is good, run the engine in the dark tonight, and look for any arcing occurring around the sparkplug wire.

If you have the 6 cylinder, I believe you have direct ignition, meaning you dont have plug wires, you have 6 individual ignition coils that sit over the sparkplugs, check to make sure all the coils are properly plugged in, next look to make sure they are fully seated over the sparkplugs.

If this stuff seems good, you could just have a bad spark plug, or bad coil, but a coil will usually throw its own code. (not always but usually).

There is a slim chance that your O2 sensor code is being caused by this misfire. Not defintely, but possible. I would probably throw a new plug in it and see how it does.